This invention relates to a scaffold used by workmen to stand and sit on or to support things when they are working, particularly to a safety scaffold which can be disassembled and reassembled and has a novel locking means to make the scaffold more stable.
A typical scaffold is shown in FIGS. 1 and 2, wherein four vertical struts 10 of L-shaped cross-section hold horizontal shelves 22 at appropriate intervals by means of horizontal bars 20 incorporating vertical mounting members 21 and brace members 23. The vertical mounting members 21 are provided with hook means 24 which engage in the appropriate attachment holes 11 of the vertical struts. The attachment holes 11 are provided at intervals along the length of the vertical struts so that the level of the shelves 22 can be adjusted. For easy access to the attachment holes 11, these holes 11 are substantially in an oblong shape. The oblong holes 11 cannot keep the hook means immobilized since there is a relatively large space around the hook means to permit its movement. Consequently, the shelf supported by the horizontal bar which in turn is held in position by the engagement of the hook means and the attachment holes cannot be kept stable effectively. For instance, when one stands on one side of the shelf, the other side of the shelf as well as the hook means below it will be caused to rise to some extent (the directions of the movement of the shelf are shown by arrows in FIG. 2). Such a condition wll sometimes make the hook means release from the attachment holes, causing the shelf to fall down.